ABSTRACT
Head injury • Extradural haematoma: classic lucid interval; not necessarily associated with
cortical damage if evacuated in a timely manner; classically, an arterial injury stripping pericranium away from the skull (mass effect increases ICP)
• Subdural haematoma: the result of tearing of dural bridging veins; indicates underlying cortical damage (mass effect increases ICP)
• Subarachnoid haemorrhage: usually the result of direct contusional injury to the brain and not the result of rupture of an underlying vascular malformation (aneurysm/arteriovenous malformation) (blockage of arachnoid granulations impairing CSF reabsorption, along with cerebral oedema, as a result of hypoxia increases ICP)
Brain
CSF
Blood
CPP mean arterial pressure (MAP) ICP
where MAP one-third of pulse pressure diastolic blood pressure
Thus, either decreasing ICP or increasing MAP should increase CPP. This relationship holds true only for brain in which cerebral autoregulation is lost, as in traumatic brain injury.
